1. Field of the Invention
The present invention relates in general to data storage systems, and more particularly to apparatus, method and computer program product embodiments for providing synchronous and asynchronous mechanisms combined with continuous data protection.
2. Description of the Related Art
Data backups are mechanisms well known in the industry that are used to allow users to restore their data due to failure of a component, human error, software corruption, or some other type of disaster. However, when traditional data backup needs to be recovered, the process can result in loss of data, as the recovery point of the data is limited to the point in time represented by the last backup. If recovery is needed to a point in time that is closer to when the disaster occurred, then more frequent backups are required. Continuous mirroring of data is also a common deployment in the preservation of data as it provides the ability to recover from a loss of access to data due to physical device failures, loss of power or networking, and other disasters. Synchronous mirroring, in which 2 or more copies of the data are preserved before informing a host that the writing of the data is complete, can provide a recovery point with no data loss. Although synchronous mirrors are very robust against physical events, they remain vulnerable to logical data errors or viruses, which are propagated automatically and quickly to the mirror target, rendering both copies of the data invalid.
Alternate disaster recovery deployments to protect data include asynchronous replication which has the advantage of allowing significantly longer distances between a primary (production) site and a secondary (disaster recovery) site to prevent loss of data resulting from a metropolitan disaster. However, the main disadvantage of an asynchronous solution is that it cannot guarantee that there is no data loss. Some amount of data in transit is usually lost when there is a failure at the primary site or within the networks connecting the two sites. The amount of data lost depends on distance, available bandwidth between the sites, and specific asynchronous implementation characteristics but can range from seconds to hours of lost data.
In order to capture the benefits of both distance and zero data loss, many users deploy more complex combinations of both a synchronous and asynchronous replication method. This however adds complexity and expense to the overall disaster recovery solution, and still does not protect against software corruption, human error, or viruses because these are replicated to the secondary site.